VMS Help CC, Messages, VALUEPRES *Conan The Librarian (sorry for the slow response - running on an old VAX) |
Message <Context> the conversion of the unsigned char/short value "<expression>" to signed int shows one example of this program's use of value-preserving integral promotion. This differs from the unsigned-preserving semantics of some older C compilers. Description This expression shows one of possibly many places where this compilation uses value-preserving semantics for small integer promotions rather than unsigned-preserving semantics used by some older compilers. In cases where an unsigned char or unsigned short int is promoted to an integer, there are two different ways the convert could happen. Standard C requires that the type be converted to a signed int (value-preserving semantics) while some older compilers will convert to an unsigned int (unsigned-preserving semantics). The difference in the choice of int or unsigned int can have an impact on results of expressions that use the converted value. The compiler cannot determine whether or not a particular instance of this usage will cause an observable behavior difference in the program. For more information, consult Section 3.2.1.1 of the Rationale for ANSI C. User Action Be aware that older, non-standard compilers might interpret this expression differently.
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